Astrophysics > Earth and Planetary Astrophysics

Title:Formation of Terrestrial Planets

Abstract: The past decade has seen major progress in our understanding of terrestrial
planet formation. Yet key questions remain. In this review we first address the
growth of 100 km-scale planetesimals as a consequence of dust coagulation and
concentration, with current models favoring the streaming instability.
Planetesimals grow into Mars-sized (or larger) planetary embryos by a
combination of pebble- and planetesimal accretion. Models for the final
assembly of the inner Solar System must match constraints related to the
terrestrial planets and asteroids including their orbital and compositional
distributions and inferred growth timescales. Two current models -- the
Grand-Tack and low-mass (or empty) primordial asteroid belt scenarios -- can
each match the empirical constraints but both have key uncertainties that
require further study. We present formation models for close-in super-Earths --
the closest current analogs to our own terrestrial planets despite their very
different formation histories -- and for terrestrial exoplanets in gas giant
systems. We explain why super-Earth systems cannot form in-situ but rather may
be the result of inward gas-driven migration followed by the disruption of
compact resonant chains. The Solar System is unlikely to have harbored an early
system of super-Earths; rather, Jupiter's early formation may have blocked the
ice giants' inward migration. Finally, we present a chain of events that may
explain why our Solar System looks different than more than 99\% of exoplanet
systems.

Comments:

Review to appear as a chapter in the "Handbook of Exoplanets", ed. H. Deeg & J.A. Belmonte